Electrochromism is a phenomenon in which a material exhibits a reversible electrochemically-mediated change in an optical property when placed in a different electronic state, typically by being subjected to a voltage change. The optical property is typically one or more of color, transmittance, absorbance, and reflectance. One well known electrochromic material is tungsten oxide (WO3). Tungsten oxide is a cathodically tinting electrochromic material, which transitions from clear (non-colored) to tinted (typically blue) by electrochemical reduction. It transitions from tinted to clear by electrochemical oxidation.
Electrochromic materials may be incorporated into, for example, windows and mirrors for residential, commercial, vehicular, and other uses. The color, transmittance, absorbance, and/or reflectance of such windows may be reversibly changed by applying a charge or potential to the electrochromic material. A small voltage applied to an electrochromic device of the window will cause it to darken; reversing the voltage causes it to lighten. This capability allows control of the amount of light that passes through the windows, and presents an opportunity for electrochromic devices or lites to be used as energy-saving devices.
While electrochromism was discovered in the 1960's, electrochromic devices, and particularly electrochromic devices or lites, still unfortunately suffer various problems, and industries have only recently begun to realize their full commercial potential.